RESEARCH SUMMARY 



A live fuel moisture model has been developed for the 1978 National Fire 

 Danger Rating System (NFDRS) to provide more analytical and consistent 

 moisture content estimates for herbs, shrubs, and grasses than was available 

 with the 1972 NFDRS. This algorithm replaces the herbaceous vegetation 

 transects used for the 1972 NFDRS. 



Weather parameters are used to calculate moisture estimates for annual 

 or perennial herbaceous plants and the leaves and twigs of small woody shrubs. 

 The parameters are daily observations of maximum and minimum relative 

 humidity, maximum and minimum temperature and hours of precipitation 

 duration. 



Because plants adapted to different environments respond differently to 

 rainfall anomalies, the United States has been divided into four climate classes 

 to provide a selection of drying rates by climate tj^e (semiarid, subhumid, 

 humid, wet). This permits adjusting seasonal moisture profiles for specific 

 locations. 



The amount or load of herbaceous vegetation is transferred between the 

 live and the 1-hour time lag (dead) fuel category as a function of the live 

 herbaceous plant moisture content. This capability utilizes improvements , 

 in the mathematical fire spread model that permits Living vegetation to act 

 as either a heat sink or a heat source, depending on whether these fuels are 

 ignited in the fire front. 



CONTENTS 



Page 



INTRODUCTION 1 



LIVE FUEL MOISTURE ESTIMATION~1972 NFDRS 1 



Woody Fuels , 1 



Herbaceous Fuels 2 



THE LIVE FUEL MOISTURE MQDELS~1978 NFDRS 3 



General Model Development 7 



Herbaceous Fuel Moisture 7 



Woody Fuel Moisture Model 13 



APPLICATION OF THE LIVE MOISTURE MODEL 15 



PUBLICATIONS CITED 17 



